Distributed optical sensing technology is turning out to be suitable for a number of downhole applications ranging from temperature sensing to passive seismic monitoring. As engineers develop new and improved systems to increase performance and sensitivity, they have encountered certain obstacles. For example, recent distributed acoustic sensing system designs specify the use of single-mode optical fiber to achieve adequate sensing performance, yet many existing well installations employ multi-mode optical fiber, which would be largely infeasible to replace. The inventors are unaware of any existing system that exploits multi-mode optical fiber for distributed acoustic sensing.
It should be understood, however, that the specific embodiments given in the drawings and detailed description thereto do not limit the disclosure. On the contrary, they provide the foundation for one of ordinary skill to discern the alternative forms, equivalents, and modifications that are encompassed together with one or more of the given embodiments in the scope of the appended claims.